1. Field of the Invention
The present invention relates to a method for regenerating a cylinder of an electrophotography photosensitive drum used in an image forming apparatus of electrophotography type, a method for producing the photosensitive drum employing the method, and a bulging apparatus for executing the methods.
2. Related Background Art
Generally, an image forming apparatus of electrophotography type such as a laser beam printer, a facsimile apparatus, a printer, and the like is, as shown in FIG. 13, provided with a cleaning blade 104, a charged roller 105, a developing roller 106 and a transfer roller 107, which are positioned with high precision in the order named around the circumference of an electrophotography photosensitive drum (hereinafter referred as "photosensitive drum") 101 consisting of a cylinder 102 and a photosensitive film 103 covering the peripheral surface thereof. For example, precision of arrangement of the photosensitive drum 101 and the developing roller 106 is such that the developing roller 106 is fixed so as to have a uniform clearance of 0.2 to 0.4 millimeter from the photosensitive drum 101, wherein precision of uniformity of said clearance is required to be in the order of a tenth part of the width (distance) of the clearance. Therefore, the cylinder 102 used as the photosensitive drum 101 is required to have high mechanical precision. In addition, impurities contained in the materials which constitute the cylinder 102 must be strictly controlled in order to form an excellent photosensitive film 103.
Therefore, the cylinder 102 should be very expensive, and regeneration thereof is desirable.
Accordingly, the following regeneration methods have been proposed.
(a) A method in which the photosensitive film of a used cylinder is removed by etching, and then a photosensitive film is formed again so as to prepare a photosensitive drum having the same outer diameter as before (see Japanese Laid-Open Patent Application No. 2-178671). PA1 (b) A method in which a cylinder has a double structure consisting of an outer cylinder and an inner cylinder, which are separable from each other, so that only the outer cylinder coated with a photosensitive film is replaced by a new one (see Japanese Laid-Open Utility Model Application No. 63-49548).
On the above-mentioned conventional techniques, the method (a) performs a heating process in vacuum in the etching step of removing the photosensitive film. So, machining time is long and productivity is low. In addition, since chemicals are used, waste liquid treatment is necessary.
On the other hand, the method (b) has to maintain mechanical precision such as circularity of the outer cylinder, and so on. Therefore the thickness of the outer cylinder cannot be thinner than a certain limit, wherein the portion to be disposed is large and cost merit is small.